Very sorry about your dog. It hurts to lose a beloved pet.

How much light is it getting? Outside or inside? What makes you think it shows signs of underwatering? I think the soil looks damp now.

In the picture I had just watered it but it's indoors on my bedside table about 8 feet away from my window (it's facing north east). In the morning hours my room gets pretty bright but after about noon or so it starts getting a little less light. I feel like it's being underwatered because of how some of the leaves on top and the long tail/vine thing are becoming shriveled and dry.

If the base is squishy, it's rotting and you'll have to take a cutting and re root it.

Take a wooden skewer or chopstick and put it in the soil for a few minutes. Pull it out to see it if it is damp. If it's damp, don't water.

Your plant needs more light. Do you have a window which gets more light, like south facing? If so transition slowly into that light.

If you want to put more effort into it, get a bag of cactus and succulent planting mix and a bag of perlite or pumice. Mix 50-50, repot your plant. Don't water for a day or two. When you water, let the water run out the bottom hole, I don't just water a little bit.

your plant needs bright light to full sun and fast draining soil. The morning sun it's getting, it needs all day.

Thank you so much!!!!